Why is nutritional support important?
In the fasted healthy state glycogen stores are used as the primary energy source. When glycogen stores become depleted,
which can occur quickly in strict carnivores such as the cat, amino acids are mobilized from lean muscle. However, within
days, a metabolic shift occurs toward the use of fats for energy allowing lean muscle to be preserved (simple starvation).
During illness alterations in hormone concentrations will shift metabolism to the use of proteins for energy (stressed starvation).
This results in a negative nitrogen and energy balance which has a negative impact on wound healing, immune function, strength
(skeletal and respiratory muscle) and overall prognosis. The goal of providing nutritional support is not to achieve weight
gain but to minimize loss of lean body mass and restore nutritional deficiencies. This also provides substrate for possible
healing and resolution/repair of an underlying disease process.
Anorexia vs hyporexia
Anorexia in cats may be defined as a complete loss of appetite especially due to disease. Hyporexia means a reduction in
appetite rather than a total loss. It is rare that patients that are completely unwilling to eat anything voluntarily can
be made to eat enough to meet their energy requirements and need to be provided with feeding tubes or parenteral (intravenous)
nutrition while an underlying disease process is managed. Certain practices may be employed to encourage consumption in the
hyporexic patient. It is important to assess for and correct dehydration (make sure patient is hemodynamically stable), electrolytes
abnormalities, reduce pain, address nausea before, etc implementing the following practices to encourage eating in a hyporexic
patient or even before implementing assisted enteral feedings or parenteral nutrition.
1. Ambiance: minimize stress and find a quiet, peaceful area for the cat to eat. Food should not be placed next to the
litter box. Food should be offered by someone that is not poking (doctor) or restraining the cat. Some cats are social eaters
and petting or brushing can sooth a cat during eating or before offering food.
2. Increase palatability: Canned foods may be more enticing to some cats; however there are cats that have eaten dry
food their entire lives and will not eat canned foods. Canned foods are typically higher in fat and protein. Warming to
a lukewarm temperature or body temperature may increase the aroma of the food. Older patients may have a diminished sense
of smell. Offering human foods such as chicken (canned, jarred baby food, or cooked). Canned tuna (especially in oil) salmon,
shrimp are aromatic and may entice the appetite of a cat. Make sure the cat is provided with fresh food.
3. Variety: A variety of foods may be offered to the cat, provided the cat does not have an underlying disease processes
that would increase chances of food aversion (uremic crisis). When this is done it is important to make sure that the food
is measured to that consumption can be accurately assessed.
4. Avoid poly-pharmacy: Many drugs can affect appetite causing nausea or decreasing appetite by altering taste.
5. Eliminating barriers: If a cat is made to wear an E-collar, remove it and watch the animal during eating. It is
important to make sure the patient has easy access to the food. Hand feeding can be attempted.
6. Appetite stimulants: Appetite stimulants may be unpredictable and unreliable. The most commonly used in cats are
IV diazepam (very short acting). Oral diazepam can cause idiosyncratic hepatic necrosis in cats and should not be given.
Mirtazepine and cyproheptadine are also commonly used in cats. Mirtazepine (Remeron® Merck & Co Inc, Whitehouse Station, NJ) is a human antidepressant medication that was noted to cause increased appetite
and weight gain in people. It may have anti-emetic properties in cats and is dosed on an every third day basis (1/8 to 1/4
of a 15 mg tablet every third day).